Recent advances in our understanding of sediment-to-water contaminant fluxes: The soluble release fraction

Abstract

Flux from the sediment-bed is a key element in chemical fate and transport water quality models used for rivers, lakes, estuaries and coastal oceans. These environmental chemodynamics simulation tools are being used to evaluate the effectiveness of remediating contaminated bed sediments. The options include monitored natural recovery, capping, dredging, in situ treatment and combinations of these. The chemical flux to water based on the particle processes (i.e., resuspension and setting) have traditionally been the focus of attention and it has received much study and re-development in the past decade. The recent availability of large sets of high quality particle and chemical data from several rivers containing poylchlorinated biphenyl compounds has caused a shift in thinking and a re-evaluation of the significance of the soluble release process. This process occurs when water flow conditions are unfavorable for any significant particle re-suspension. The objective of this paper is to demonstrate that a rapid soluble release process exists and to offer an algorithm for quantifying its flux from the bed. Data obtained from four major rivers show that the soluble fraction may vary from a few percent to nearly 100 percent of biphenyl release. A numerical ranking of the known and quantifiable individual soluble release processes places in-bed bioturbation first on the list. Coupled with the benthic boundary layer resistence, a simple theoretical algorithm is offered as the model for the overall mass-transfer coefficient K _f of the soluble release process. Although some laboratory and field data exist to support the algorithm, further studies will be needed in order to satisfy all members of the engineering science community.

Keywords:

• mass-transfer coefficients
• water quality models
• polychlorinated biphenyls
• bioturbation
• benthic boundary layer
• solubilization

Notes

^*Estimated from QEA (1999).

¹Karickhoff and Morris (1985)

²Reible et al. (1996).

Source: Erickson et al. (2003).

Source: Erickson et al. (2003).